This came as a surprise when it was presented at Baselworld in March 2015, because even though Patek Philippe have made a few aviation watches, they had never made anything with such a powerful classic pilot’s watch aesthetic. As a result it looks superficially like other classic pilot’s watches made by other brands.

But it is totally different to all the rest. On the dial, where you would normally find the continuous seconds subdial (as in the IWC Heritage 55), there is the date indicator. This is very smart because it reinforces the classic pilot’s watch appearance while adding the date function in a format that is far more attractive than the usual date window. The date can be adjusted using a semi-recessed pusher on the caseband between 6 and 7 o’clock.

Another fundamental difference is a patented system for showing the time in a second time zone. Local time is shown by the main hour and minute hands, while home time is shown by an additional skeletonized hand, designed so that if you don’t need the additional time zone, it hides exactly behind the hour hand. The local hour hand can be moved back or forwards in one-hour increments by using the two pushers on the left-hand side of the case, without affecting the time displayed by the minute and seconds hand. Two small circular windows at 3 and 9 o’clock show day or night for home time and local time respectively.

Patek Philippe are brilliant at making complicated functions very simple to use. One example is the time-zone adjustment pushers. They have a safety lock to prevent accidentally changing the local hour time, operated by rotating the pusher by a quarter turn.

The watch is very wearable, at 42 mm diameter and 10.78 mm thick. The case is in white gold, with a lovely dial in dark blue enamel, with white gold appliqué Arabic numerals coated with SuperLuminova for night-time visibility. The watch is powered by the Calibre CH 324 S C FUS movement designed and built by Patek Philippe, and visible through the sapphire caseback. It is mounted on a vintage brown calfskin strap with contrasting stitching. All in all, a superb example of how a familiar genre can be adapted to new functions.

The Patek Philippe Calatrava Pilot Travel Time is reference 5524, and costs 42,000 Swiss francs. It is not a limited edition, but in any case Patek Philippe don’t make many watches. For this reason, it’s probably the only brand for which a purchase of this sort can be considered as an investment.